Glow discharge devices



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cLow DISCHARGE msvrcss l4 Sheets-Sheet 13 Flt-3-7- IN VEN TOR. Dally/a: 6. [bye/kart BY ATTORNEY 2,937,317 GLOW DISCHARGE DEVICES Application May 29, 1956, Serial N0. 588,022 "48 Claims. (Cl. sis-84.6

This invention relates to gaseous discharge devices. In particular this invention'is directed toward increasing the speed of operation of gaseous discharge shifting and stepping devices.

Gaseous discharge devices have enjoyed but limited use in computer circuits mainly because of their inferior operational speed as compared to vacuum tube circuits. For example, vacuum tube counters may operate at a rate of up to 10 million counts per second; whereas, gas tube counters have been limited to a reliable operating speed of under 100,000 counts per second. However, where the ultimate in speed is not required, gas tube devices, particuarly the cold cathode type, offer advantages of low. power consumption, simplified circuitry, and lower overall cost. a

One of the important limitations on the operational speed of gaseous discharge counter or registers is the deionization or glow decay time. It has been discovered that when electric fields at certain frequencies are applied to a volume of ionized gas, deioniza-tion is hastened and thus operational speed is increased. The present invention is directed to the application of these electric fiields and is described, by way of example, in connection with a glow discharge shifting register of the type disclosed in my copending application Serial No. 521,555, filed July 12, 1955, now US. Patent'No. 2,923,853, issued February 2, 1960. Briefly such a shifting register comprises a gas-filled tube and three arrays of electrodes associated with the tube defining a plurality of glow discharge positions which may sustain a glow at one time. High frequency potentials sequentially appliedto the electrodes cause a stepping or shifting of a pattern of glow discharges in the tube. In other words, each glow discharge is shifted from one discrete glow discharge position to a successive glow discharge position during each cycle of operation of the device. The interval of one operation cycle thus corresponds to a digit interval. In such a shifting register, a binary "1 may be represented by the'presence of a glow discharge and a binary by the absence of a glow discharge or vice versa. Thus, a pattern of glow discharges represents a binary word.-

Glow shifting is effected and controlled by applying the principle of priming which requires that the operating voltages applied to the tube be in the sustaining voltage range, that is, between breakdown voltage and extinction voltage. The breakdown voltage may be defined as that voltage Which mustbe applied across a gas in a given case to initiate a glow discharge. The glow discharge can be sustained by a voltage somewhat below the breakdown voltage but if the voltage is lowered sufiiciently, the glow dies out at a voltage called the extinction voltage. Thus when a first eelctrode is connected to a sustaining voltage, an initiated glow discharge is maintained. An adjacent, second electrode can be positioned such that the gaseous atmosphere in the re gion of influence of the second electrode is partially ionized due to its proximity to the glow discharge held by the first electrode. If a sustaining voltage is applied nited States Patent 0 2,937,317 Patented May 17, 1960 to such a primed electrode, it picks up a glow; whereas an unprimed electrode energized with the same potential remains inactive and does not pick up a glow. For proper operation of a glow discharge shifting or stepping tube,the operating voltages applied to the electrode arrays must be within the sustaining voltage range. If the operating voltages drop below the extinction voltage, the glow discharges will, of course, die out and be lost; if the operating voltages rise above the breakdown voltage, spurious glow discharges will occur at unprimed electrodes.

As previously mentioned, a primary limitation on the operational speed of gaseous discharge counters and registers is the deionization or glow decay time. Glow decay time may be defined as the time required, subsequent to the removal of a sustaining voltage from an electrode holding a glow discharge, for the ionization level to decrease to the extent that re-application of the sustaining voltage to the electrode will not revive the glow discharge. In other words, it is the time required 'for the ionization of the gaseous atmosphere associated with the electrode to drop below the priming level. 1

Glow decay time 'is influenced by such factors as gas composition and pressure, and particularly by vessel dimensions. The process of deionization is not completely understood, but it is thought that for the low-pressure gaseous discharge, deionization'is mainly a process of diifusion of the electrons and ions to the vessel walls (and to the .electrode surfaces in the case of internal electrodes). For example, experiments with external electrode glow shifting tubes, energized with high frequency, show that the glow decay time is less with tubes of small diameter than with tubes of large diameter.

It has been found that the difiusion process can be accelerated, thereby decreasing the glow decay time and increasing the operational speed, by subjecting the deionizing gas to appropriate electric fields. These fields apparently help to disperse the ionized particles, or plasma, by sweeping the charges to the vessel walls. The electric fields may be applied to the gas by external electrodes and may be developed by an alternating potential at an appropriate frequency or by a DC. potential change at the appropriate time in an operating cycle.

-A voltage thus applied to shorten the glow decay time isv referred to hereinafter as a quench voltage.

The optimum magnitude and optimum frequency of a quench voltage cannot be generally specified at this stage of development, but these parameters are dependent on the dimensions involved "and, in particular, upon the capacity between the electrodes and the inside walls of the vessel. The magnitude of the quench potential must be low enough not to cause appreciable ionization, and the frequency must below enough to induce displacement oscillations of suificient magnitude to sweep out or difing tube.

fuse the ionized particles. Practical quench potentials and also practical energizing potentials may be determined, in a particular case, by routine experiment in .view of the examples hereinafter presented.

'It is, therefore, a general object of the present invention to rapidly deionize an excited region of a gaseous atmosphere.

Another object is to increase the speed of operation of a gaseous discharge stepping device.

. A further object is to rapidly shift a glow discharge in a gas-filled channel.

Another object is to enter a selected discharges into a gas-filled channel.

' Another object is to provide an improved glow shiftpattern of glow Another object is to provide a glow discharge shifting register which can be reliably shifted at speeds in ex cess of 100,000 cycles per second.

Another object is to simultaneously register a binary word and the complement of the word.

A further object is to provide a multi-position gaseous discharge shift register comprising a single unit of small size, low cost and of relatively high speed.

The underlying principle of the present invention is theapplication of a quench voltage to a decayinggaseous discharge to hasten difiusionof the plasma and thereby shorten the glow decay time.

Other objects and principles will appear from the following description, reference being made to the accompanying drawings wherein:

Fig. 1 is an illustration of an. axial-field. glow shifting tube with a block diagram of associated circuits including a quench potential generator;

Fig. 2 is a timing diagram of a one-cycle shift. sequence of the device of Fig. 1;

Fig. 3 shows generally how energizing potential varies with applied frequency;

Fig. 4 is a schematic diagram erator;

Fig. 5 is an illustration of a glow discharge. shifting tube and a block diagram of an energizing circuit for providing selective quenching;

Fig. 6 is a cross section of the tube of Fig. 5 along the lines 6-6 showing the placement of the internal readout electrodes;

Fig. 7 is a timing diagram of a one-cycleshiftsequence of the device of Fig. 5;

Fig. 8 is an illustration of an alternate form of 1a selectively quenched glow discharge. shifting tube. with a block diagram of associated operating circuitry;

Fig. 9 is a cross section of the tube of Fig.8 along the lines 9-9 showing the placement of an alternate form of internal readout electrodes;

Fig. 10 is a timing diagram of a one-cycle shift sequence of the device of Fig. 8;

Fig. 11 is a front view of a glow discharge shifting tube in helical form with external electrodes arranged for selective quenching;

Fig. 12 is a right side view of the device shown in Fig. 11;

Fig. 13 is a diagramatic representation of a glow discharge shifting tube having no internal electrodes and a block diagram of an energizing circuit including circuitry for applying a D.C. quench voltage;

Fig. 14 is a timing diagram of a one-cycle shift sequence of the circuit of Fig. 13;

Fig. 15 is a schematic diagram of a two-level signal generator;

Fig. 16 is a schematic'diagram of a D.C. amplifier for use with the device of Fig. 13;

Fig. 17 is an embodiment of the invention for simultaneously registering a word and its complement;

Fig. 18 is a schematic diagram of a signal generator as employed in the device of Fig. 17 for developing both a high frequency energizing potential and a D.C. quench potential;

Fig. 19 is a timing diagram of a one-cycle shift sequence of the device of Fig. 17;

Fig. 20 is a schematic diagram of a damped wave quench frequency generator; and

Fig. 21 is an' illustration of an output waveform of the generator of Fig. 20.

A gas tube shifting register utilizing high frequency energized external electrodes to maintain and shift any reasonable number of glow discharges is shown'in Fig. l. A glow discharge channel formed, for example, of transparent material such as glass, is filled to alow pressure with an ionizable gas such as neon. External elecof a suitable signal gentrod-es are formed as rings on bands around the tube.-

Alternate :bands 28 areconnected togetherxand to a.low frequency quench voltage source shown as LF generator 38. Since bands 28' are at ground or at a "reference potential, they may be collectively referred to as :1 reference electrode. Electrodes 25, 26, and 27 comprise first, second and third iterative arrays of energizing electrodes and are positioned in sequentially alternate arrangement between bands 28'. Electrodes 25 are connected by a lead 20 to a normally On source of energizing potential shown as HF generator 31. The energizing potential is at a sustaining level; thus, during periods between operating cycles, any glow discharges which have been entered into, the tube are held active byelectrodes 25. Therefore, electrodes, 25 are designated holding electrodes and each electrode 25 thus defines a discrete flow discharge position coresponding to an order of a binary word. Electrodes 26 and 27 aresequentially interposed between holding electrodes 25 and are connected, by leads 21 and 22, to respective, normally Off, HF generators 32 and 33. Electrodes 26 and 27 perform the shifting of a glow discharge from one holding electrode tothe next and are therefore designated shifting electrodes. A pair of stabilizing electrodes, shown as internal electrodes 29 in Fig. 1, provide a constant glow discharge in the input end of the tube. The stabilizing electrodes maintain a substantially constant quiescent ionization level in the tube and also prime a transfer electrode 24. Transfer electrode 24: is connected by a 1ead23 to a normally OE HF generator 30. When .the. transier electrode. is energized, by a sustaining potential .trom HF generator 30, it picks. up a glow from electrodes 29 and primes the first holding electrode 25(1), thus providing entry into the shifting register. Operation of the gas tube register will be described in more detail after the following discussion of the elements comprising the energizing circuit.

The energizing circuit comprises HF generators 30 to 33, and LF generator 38. These generators are controlled. by a circuit comprising a trigger circuit 34, and univibrators 35 and 36. Trigger circuit 34 may be, for example, an ordinary Eccles-Jordan type of bistable circuit such as shown in Fig. 2.36 of Electronics, by Elmore and Sands, National Nuclear Energy Series, Division V, volume 1', McGraw-Hill, 1949. Univibrators 35 and 36 are ofthe well-known type which provide an output pulse of selectable duration in response to each input pulse. A suitable univibrator is shown in Fig. 2.33 of the above reference.

The energizing signalgenerators 30 to 33 and 38 may take a variety of forms. One suitable embodiment of signal generator is shown in Fig. 4. A tube 63, shown for example'as a duotriode, is connected in atuned-plate, tuned-grid oscillator circuit. A keying; tube 55 is provided to control the oscillator. By suitable selection of the potential of a keying tube control grid bias source -C, the generator can be operated either as normally Off or normally On. Consider, for example, the case where battery 52 is 250 volts and the bias potential C is also 250 volts. Since the keying tube grid and cathode are then at the same potential, the tube 55 will normally conduct, thereby applying a relatively high negative potential, or blocking bias, through a grid tank coil 56 to the grids of the oscillator tube 63, thus rendering the oscillator inoperative. A negative potential of suitable level applied to a terminal 50 will key the circuit to operation by cutting oii conduction in the keying tube 55, thereby removing the blocking bias from the oscillator grids. The signal generator may be operated as normally On by adjusting the bias potential C.to keep the keying tube 55 at cutoff and thus the oscillator in operation. A positive potential applied to terminal 50, under these conditions, causes the keying tube to conduct thereby biasing the oscillator to an inoperative or OE state.

Output is taken from the signal generator at a pair of terminals 61 and 62 connected to a coil 60 that is coupled to a plate tank coil 59;terrninal 62-is grounded when single-ended output is desired. The tank circuit generator 32 (Fig. 1), which is .lead 22 (Fig. 1).

constants of the oscillator are,'.of course,"chosen to give the appropriate signal frequency; i.e., a relatively low frequency in the case of LF generator 38 (Fig.' 1) and 'a relatively high frequency for HF generators 30-33. As

previously discussed, the optimum energizing and quench frequencies are dependent on the physical characteristics \of the glow shifting tube.

In an example of parameters of the embodiment shown in Fig. l, the tube is 3 mm. outside diameter (0.6 mm. wall thickness) glass tubing filled with neon to a pressure of 7.5 mm. of Hg. The electrodes are No. 18 wire rings spaced about one-quarter inch apart. Energizing frequencies are not critical, and frequencies above megacycles may be conveniently employed. Below about 10 megacycles, impractically high energizing voltages are required for the tube of the. present example. Thus, an

energizing potential of about megacycles at about 100 volts R'.M.S. is used as a compromise between the high voltages required at lower frequencies (see Fig. 3) and the problems, such as stray capacity effects and difiiculties in generating power, attending with the use of very high frequencies. Also, for a given tube, as the energizing frequency is raised, the energizing voltage required may become impratically high, and the ratio of breakdown voltage to extinction voltage may also become impractically low. The general shape of a curve comparing energizing potential vs. frequency is shown in Fig. 3.

The optimum frequency of the quench potential is considerably lower than the frequency of the energizing potential. In the present example the most advantageous quench potential is found to be about 100 volts R.M.S. in the range of 1.5 to 2.5 megacycles.

It should be noted that the quench generator 38 (Fig. 1) is in seriesv with the energizing generators 30' to 33. Therefore, generator 38 should present a loW impedance to the energizing frequency and, conversely, the energizing generator should present a low impedance to the quench frequency. 'Also, in the circuit shown in Fig. 1, the keying tube 55 (Fig. 4) and'its circuit are not required since the quench generator operates continuously.

Operation of the gas tube shifting register of Fig. 1

will now be described in detail by assuming, for example, that it is desired to enter the binary Word 101 into the tube. The word may be entered either lowest or highest order first.

At the beginning of each digit interval or shift cycle,

a shifting pulse from a suitable source is applied to a lead 45. This shifting pulse may be a clock pulse from an associated computer as, for example, from terminal OP (Fig. of copending application Serial No 458,473, filed September 27, 1954, by George B. Greene et al. A shifting pulse source is illustrated in Fig. 1 by a battery 42, a capacitor 41 and a single-pole, double-throw switch 40. When switch is momentarily closed to the right, a pulse is applied to lead 45. This pulse sets trigger circuit 34 and simultaneously triggers univibrator 35. v The HF generator 31 is normally On to thereby apply a holding potential to holding electrodes 25 through lead 20. When trigger circuit 34 is set by the. shifting pulse it keys HF generator 31 Off, thereby removing the holding potential from electrodes 25, as shown graphically by the HF envelope E in Fig. 2. At the sametime, HF normally Off is keyed On by univibrator'35, thereby applying a potential E (Fig. 2) to the shifting electrodes 26. When univibrator 35 (Fig.1) returns to its normal state, HF generator 32 returns to its normal 01f condition. In returning to its normal state univibrator 35 gen- ..erates a pulse which is transmitted through a lead 37 to trigger univibrator 36. Univibrator 36 transmits a keying potential to HF generator 33, thereby energizing shifting electrodes 27 by applying potential E (Fig. 2) through The triggering potential from univibrator 36 is also applied to a lead 43 which is connected entered 1 value.

to a switch 39 in the input of HF generator 30. Switch 39 is the value input switch, shown by way of illustration as a manuallyoperated switch. Obviously, it may be an electronic switch or gate appropriately controlled; as, for example, from the 1s transfer bus (Fig. 32) of the above-mentioned copending application Serial No. 458,473. In any given digit interval, if the value to be entered is a 1 then switch 39 is closed. Conversely, switch 33 is left open if the value to be entered is a0. In the present instance, it is assumed that the binary word 101 is to be entered. Thus the value for this first digit interval is a l and therefore switch, 39 is closed to apply the keying potential from univibrator 36 to normally Ofi' HF generator 30. The output of HF generator 30 is connected to the transfer electrode 24 through a lead 23. When energized the transfer electrode 24 picks up a glow from the stabilizing electrodes 29. When univibrator 36 returns to its normal state, shifting electrodes 27 and transfer electrode 24 are tie-energized; a pulse is transmitted from univibrator 36 through a lead 44 to reset the trigger circuit 24, thereby keying HF generator 39 On and returning the holding potential (E .Fig. 2), to holding electrodes 25. The first holding electrode 25(1), adjacent the transfer electrode24, is primed by the energized condition of the transfer electrode. IJpon being re-energized, the holding electrode 25(1) captures and holds a glow discharge to represent the This glow discharge at electrode 25( 1) primes the adjacent shifting electrode 26(1).

The second digit in the binary word 101 is a 0, to be entered during the second digit interval, or shifting f cycle. Asbefore, momentarily closing switch 40 to the vibrator 36 appears on lead 43;however, since the value to'be entered in the present digit interval is a 0, switch 39 is left open and transfer electrode 24 remains de-energized. Univibrator 36 now returns to its normal state, de-energizes shifting electrodes 27, and develops a pulse on lead 44 to reset trigger circuit 34 and return the energizing potential to holding electrodes 25. Consequently, the single glow discharge is further shifted from electrode 27(1) to 25(2). Therefore, at the end of the second shift cycle, a glow discharge held at electrode 25(2) represents the input digit 1 of the first digit interval and the absence of a glow at holding electrode 25( 1) represents the input digit "0 of the second digit interval.

The highest-order digit of the example word 101 is a l," and this digit is entered into the shifting register tube in the manner described above in relation to the lowest order digitl. Thus, at the end of three digit intervals, the word 101 is represented by a glow at electrode 25(3), no glow at electrode 25(2) and av glow at 25(1).

If successive shift pulses are now applied to lead 45, it

is clear that the established glow pattern will be shifted by one position to the right during each shifting cycle until eventually it reaches the rightmost end of the tube.

Readout from the register is shown in the form of aphotoelectric tube 48 positioned to detect a glow held by electrode 25 (n). The glow pattern is shifted through electrode 25(n) and is lost, with the readout device detecting each glow and giving an output at terminal 4.6 in response thereto. The example word. 101 thus appears on terminal 46 in the same order as entered, with-ls .represented by an output signal and "0s represented by an absence of 'such an output signal. 7

The LF generator 38 continually applies a quenching 124 is positioned near potential be ween-reference electrodes 28' and. each energizing electrode 24 toZ7. Therefore,.the quenching signal is continually active to disperse any ionization and thus-to decrease the glow decay time, permit-ting at least a three fold. increase in operatingspeed. It is clear that the quenchingsignal as-applied in Fig. 1 not only acts to disperse a .decaying glow discharge but it alsoacts upon a-sustained glow. For this reason somewhat morepoweris, in general, required of the energizing generators in the .embodimentshown in Pig. 1 to-overcome the influence of the. quenching signal when a glow is shifted'or held.

The power loss :dueto thenecessity ofovercoming the quenching-signal is eliminated in the embodiment shown in-Fig. 5 through the useof a technique of selective quenching; i.e., only .the unexcited electrodes are subjected-to a quenching signal. Theglow shifting tube ofFig. 5. also. employs a transverseelectrode, structure to obtain airelatively high.capacity .between electrodes and the gas in the tube. The increased capacity improves the quenching. These external electrodes may be formed of any conducting material. Where the tube is formed of 6 mm. glass tubing and filled toa pressure of 7.5 mm. of Hg with.neon,.electrodes about one-quarter inch wide,

spaced from each other about three-sixteenths of an inch :4

and formed to the curvature of the tube along approximately one-quarter of the circumference are-found satisfactory. Alternatively, the electrodes may be plane and of approximately, the outside diameter of the tube in length asillustrated in Fig. 6.

The energizing circuit of this embodiment is similar to. the energization circuit of -Fig. l. Transfer electrode theend. of the tube so that it is .primed by the stabilizing electrodes 29. Holding electrodes 25 and shifting electrodes 26 and 27 arepositioned along the tube in a sequentially alternatearrangement and connected to respective energizing generators 31 to 33. A similar-electrode structure comprising a plurality of reference electrodes 71, 72 and 73 is arranged along the opposite side of the tube with electrodes 71, 72 and 73 positioned to cooperate respectively with electrodes 25, 26 and 2 One of the electrodes 73 is positioned to cooperate with the transfer electrode 24. Eachelectrode array 71, 72 and 73 is connected, by a respective lead 77, 78.a nd 79 to a respective quenchfrequency generator .74, 75 M76. The.quenchgenerators .are connected by respective leads 81, 80-and 49 to appropriate points in thecontrol circuit, and are controlledtogetherwith, but inversely. to the energizing generators 31, 32 and 33. For .example, quench generator 74 .is Off when energizing generator 31 is On and vice versa.

Fig. 7 illustrates typical operating potential envelopes for a one-shift cycle of theregister of-Fig. 5. The holding potential E and the quench potentials E and E are normally On. When the holding potential E is keyed Oil, the associated. quenching potential E is keyed On. The first shifting potential E is also keyed. On and the associated quench potential E is keyed Off. Similarly, when the second shifting potential E is keyed On, the associated quench potential B is keyed Off. In each case, an energizing potential and its associated quench potential are inversely controlled so that. only the decaying glow discharges. are subjected to the quenching potential. Comparing the energizing potential envelope E and the quench potential envelope E (Fig. 7), for example, it is apparent that the quench potential generators areadjusted to give somewhat longer rise times than the energizing generators. This is to assure that any primed energizing electrode picks up a glow before the ionization is quenched to below priming level.

Fig. .5 also illustrates a pair of internal readout electrodes 82 and 83 positioned in the region of influence of the rightmost holding electrode 25 (n). The use of internal readout electrodes rather. than the photoelectric readout of Fig. 1 permits the vessel to be formed of any shift register is illustrated in Fig. 8.

r are turned On, thereby causing suitable material whether. transparent or not. .Also, it shouldbenoted that the circular crossIsectionof the glow discharge channel is not" an essential feature of the invention. Glow discharge channels .may, for example, be formed in ceramics or certain plastics and have square, rectangular, or other cross section. A crosssection view of the tube (Fig. 6) shows the axial location of these internal electrodes. It is seen that the readout electrodes are asymmetrically positioned in the. tube; therefore, when a glow discharge is heldbetween holding electrode 25(n) and reference electrode-71m) the readout electrodes are in planes of different potential in the glow discharge plasma. This potential difference between the readout electrodes causes a current flow through a relatively high resistance 84. v The consequent voltage drop across resistor'84 constitutes the readout signal, which is available at a pair of terminals and '86.

Another form of a selectively'quenched glow discharge As compared to Fig. 5, it will be noted that the reference electrodes 71, 72 and 73 are shifted laterally and positioned to overlap adjacent energizing electrodes. The control and energizing circuitry is similar to that of Fig. 5 with the exception of the control connections to the quench potential generators 74, 75, and 76. In the embodiment shown in Fig. '8, low frequency generator 76 is controlled together with HF generator 31 by the potential from the output of trigger circuit 34. Similarly, low'fi equency generator 74 is controlled together with HF generator 32 by an output from univibrator 35 and low frequency generator 75 is controlled together with HF generator 33 by univibrator .36. Therefore, as shown in the timing diagram of Fig. 10, the energizing potential E and quench potential E are normally On.

Glow discharges may be entered into the tube through the agency of transfer electrode 24 in the 'manner previously described. An entered glow discharge held by electrode 25(1) is illustrated by a dashed ellipse 1 Within the tube. At the beginning of a shift cycle, potentials E and E are turned Oil and potentials E and E are turned On. Thus the glow discharge. steps to a position illustrated at 2 (Fig. '8). Subsequently, potentials E and E are turned Olf. and potentials E and E m I a further shift. of the glow dischargeto the position illustrated at 3. Finally, potentials E and E .are returned and potentials E and E are turned Off, and at the end of the shift cycle, theglowdischarge is held by electrode 25(2), asillustrated at 4. r

.Readout from the register of ,Fig. 8 is by way. of a pair of internal electrodes 87 and 88. A cross-section view (Fig. 9) shows that these electrodes are symmetrically positioned in the tube; i.e. they are positioned in an .equipotential plane. When electrode 25(n) is not holding a glow, a relative high impedanceeXistsbetWeen a pair of output terminals 89 andv 90 connected to respective readout electrodes. However, when electrode 25(n) is holding a glow, the impedance across output terminals 89 and 90 is relatively low. This impedance drop constitutes the output signal.

Figs. 11 and 12 illustrate a helical form of a glow discharge shifting tube adapted for selective quenching. The helical tube is essentially a rolled up axialfield design and it offers particular advantages since its electrode structure is especially simple to construct. The electrodes are formed by strips or hands looped longitudinally around the turns of the helix. Fig. 12 is a right-end view of thetube as shown'in Fig. 11. Fig. 12 shows the arrangement of electrodes and the connections to energizing and control circuitry. Such circuitry may be as shown inFig. 8 and analogous reference numbers are accordingly applied to Figs. .11 and 12. For example, electrode 71' of Fig. 12 is analogous to the ele ct rodes 71 ofFig.8. ii I i i Y a low time constant. circuit output must present a low impedance to the en- 9 'A further embodiment'of the present invention, shown in Fig. 13, employs a change of D.C. potential level as the quench potential. The D.C. quench has the most desirable feature of the selective A.C. quench (Figs. and 8) because only decaying glow discharges are subjected to the quench effect. The D.C. quench also has circuit simplicity comparable to the constant A.C. quench (Fig. 1).

The energizing circuit of Fig. 13, comprising HF generators 3 -1 to 33, trigger circuit 34 and univibrator 35 and 36, is similar to that previously described for Fig. 1. However, input is obtained somewhat differently. In Fig. 13 the functions of keeping a glow alive in the tube and of entering values into the'tube are combined, and

v the tube has no internal electrodes. A pair of input electrodes 95 are energized by a high frequency generator 67 which operates at either of two selectable output levels. At its normal output level, HF generator 67 applies a potential across electrodes 95 to maintain a small, glow discharge illustrated at 96. The two-level HF generator 67 is controlled by an output of univibrator 35 through the previously described value input switch 39. Assuming switch 39 closed, when univibrator 35 is triggered asits abnormal state, a relatively high potential exists at its lefthand output. This potential is applied-through a lead 69 and switch 39 to bias generator 67 to a higher output level. The higher output across electrodes 95 causes the maintained glow 96 to expand as illustrated at 97, and the first shifting electrode 26 is thereby primed. Since the shifting electrodes 26' are energized by the action of univibrator 35, simultaneously with the biasing of generator 67 to its higher level, shifting electrode 26 picks up a glow which is shifted successively to the second shifting electrode '27 and then to the first holdingelectrode 25.

An example of a two-level HF generator 67 is shown schematically in Fig. 15. A pentagrid tube 100 is'arranged in a tuned-plate oscillator circuit having a plate tank circuit which comprises a capacitor 102 and a coil .103. A feedback winding 107 is connected to the third grid. Output is taken from a pair of terminals 105 and 106 connected to a secondary winding 104. Terminal 106 is normally grounded for single-ended output. A

terminal 101 is connected through switch 39 (Fig. 13) .to an output of univibrator 35. Thus, the output of univibrator 35 controls the bias on the first grid of tube 100 (Fig. 15). A change in the bias on the first grid causes a corresponding'change in transconductance of the tube and hence a change in its output level. I

The D.C. quench circuit of Fig. 13 comprises a quench control trigger circuit 92 which controls the output level of an amplifier 91. The output of amplifier 91 is connected to a reference electrode 28 common to all the energizing electrodes. The D.C. potential change-required for quenching is only about 150 volts in the present example; therefore, it is possible to eliminate amplifier 91and obtain the quench voltage directly from the trigger circuit. However, the arrangement shown eases the .design requirements. The D.C. voltage must change rapidly for efiect-ive quenching; consequently, the output of the quench circuit connected to electrode28 should have On the other hand, the. quench pedance while still supplying the necessary voltage change. g

An example of an amp1ifier-91is shown schematically 4 in Fig. 16. A pentode tube is shown with a plateload resistor 111 and a bypass capacitor 112 which provides a low impedance to the energizing potentials- An output terminal 114 is connected to the reference electrode 28 (Fig. 13) and an input terminal 113 (Fig. 16) is connected to an appropriate point of the quench control vIt) trigger circuit 92 (Fig. 13), for example, to the control grid of one of the trigger circuit tubes or to an appropriate potential point of a grid resistor.

Operation of the D.C. quenched shifting register of Fig. 13 may be better understood by reference to: Fig. 14 wherein the potentials applied to the tube during a one-cycle shift sequence are graphically shown. As in the previously discussed embodiments, a pulse is applied to lead 45 (Fig. 13) to initiate a shift cycle. This pulse sets trigger circuit 34 and triggers. univibrator 35 to its abnormal state. 'The HF generator 31, connected to the holding electrodes 25, is keyed Otf by trigger circuit 34 as shown by E (Fig. 14). A negative output pulse on a lead99 (Fig. 13) from the left side of trigger gizing potential to the first shifting electrodes as shown by E (Fig. 14). It may thus be seen that the D.C. quench level is changed after energization is substantially removed from one group of electrodes and before complete energization is applied to the next adjacent group of electrodes. In other words, it is a change in D.C. potential. applied between the envelopes of HF energization which is effective to discharges. It should be noted that the time constants associated with the various circuit elements may be adjusted to give the delays necessary to obtain the sequence of events described.

When univibrator 35 returns to its normal state, HF generator 32 is keyed Off and a negative pulse is developed von'lead 98; this pulse reverses trigger circuit 92 to again change the D.C. quench voltage level. The output pulse from univibrator 35 also is applied over lead 37 to trigger univibrator 36 to its abnormal state. Univibrator 36 keys HF generator 33 to On for energizing the 27 as shown by E (Fig. 14). A one-shift cycle is completed after univibrator 36 (Fig. 13) returns to its normal state, which keys HF generator 33 to Off, again reverses the quench control trigger circuit 92 over leads 44 and 68, and resets trigger circuit 34 to key On the HF generator 31 and return the holding potential E (Fig. 14).

The circuit of 'Fig. 13 may be modified to provide another type of DC. quench which might more appropriately be called pulse quench. Trigger circuit 92 is removed and the outputs of diodes 94 are joined and connected through a capacitor (not shown) to the input of amplifier 91. Amplifier 91 thus becomes a pulse amplifier and therefore every negative pulse applied through diodes 94 causes a positive quench pulse on the reference electrode 28. Consequently, a quench pulse is applied between energizing potential envelopes as is illustrated by the potential E in the timing diagram of Fig. 14.

Quenching by a, change in D.C. potential may be employed in the previously described embodiments of shifting registers. For example, in Figs. 5 and 8, it

is necessary only to replace eachlow frequency generator 74, 75 and 76 with a trigger circuit 92 (Fig. 13)

and its associated amplifier 91. V

Likewise, pulse quench maybe employed in the embodiments of Figs. 5 and '8 by replacing each low frequency generator 74, 75 and 76 with a capacitively,

coupled amplifier 91. In this case it is necessary to add an appropriately oriented diode in series with each control lead 49, 80 and 81 (Fig. 5) or 64, 65 and 66 (Fig.

8), since a quench pulse is desired only when an energizing generator is turned Oif. For examplein Fig. 5 when HF generator 31 is keyed Olf a quench pulse should be applied to electrodes 71; however, when HF quench the decaying glow 1.1 generator is returned On, t heelectrodes 71 "shouldn'ot be quenched, for such'a "quench"ivould operate against the excitation potential. It should be noted thatthe polarity of a quenchpulse is immaterial. Positive'or negative pulses appear to be equally efiective.

An arrangement for simultaneously registering a word and its complement is shown inFig. 17. An envelope 1135 forms two glow discharge register channels having a common gaseous atmosphere. A common gaseous atmosphere is not essential but it is desirable, because the consequent uniformity. of the gas in both. channels assures more uniform operation. The two registers are, in effect, connected in parallel except for respective transfer electrodes, .124. These electrodes are 'driven from respective HF generators 130 and 131 which are controlled in a complementary fashion. During a given shift cycle, if an input switch 139 is closed to the right (as shown), a glow is entered into the lower register and a complementary, no glow" is entered into the upper register. Conversely, if switch 139 is closed to the left, a no-glow isentered into the lower register and a glow into the upper register. Thus, if a glow discharge exists at a given position in one register, a no-glow exists at the corresponding position in the otherr'egister. A distinct advantage, of the complement .tube arrangement is that the number of glow discharges existing in the registers is constant; therefore, the loading on the driving generators is constant. Another important feature of the complement tube arrangement is the possibility of a simple error-checking output circuit since the sum of the values in each channel any order should always be 1.

Aspreviously stated, quenching may be provided by a change, at an appropriate time, in the level of a D.C. potential applied to an electrode. In the complement register arrangement of. Fig. 17, the HF generators comprise a novel circuit which also develops the D.C. quench potential. A grounded reference electrode 128 is positioned to co-operatewith all the excitation electrodes, because, in this case, both the excitation and quench potentials are applied to the excitation electrodes.

A schematic diagram of. HF generators 130 to 134 (Figl l7) is shown in Fig.18. The circuit comprises an oscillator tube 143 and a controltube 141. A coil 145 "and a capacitor 144 form the oscillator tank circuit and a coil 152 coupled to the tank coil provides feedback tothe oscillator grid. The control tube 141 operates in a rriann'erjanalg'g'ous to control tube .55.. (Fig.4), previo'u'sly described. Control tube 141 has in its. plate circuit the grid leak of the oscillator, a resistor .142. The oscillator may beoperated normally Off by. adjusting a biaspow'er supply .-C to allow the control tube to conduct sufficiently developing an oscillator cutofi bias potential across resistor 142.. If a negative potentialis applied to a control input terminal 140 under these conditions, the control tube is c'ut ofi and the oscillator goes into operation; The oscillator'may' be operated normally 'Onby adjusting the power supply -C to cutoff for the controltube 141. A positive input potential to 't'erntinal ,140 now' causes the control tube to conduct and the oscillator is therebybiased Off.

, Output istaken from the oscillator by a direct connecti'o'nfrom the plate of the tube to' an output terminal 146. In Fig. 17, the output terminal of e'achI-IF generator 130 to 134 is connected directly to a respective group of-e1e'ctrodes124 to 127. "Thus there is direct -current,coupling from an electrode (or from an array of electrodes) through thetanlc coil .145 (Fig. ,18) and through a resistor 148 to a plate supply source +13. When theoscillator is On it d'rawsj'curre'nt through're- 'sistor l tfi. Therefore, the D.C. voltage on the electrodes is the value of +13 'minus the drop across resistor 148. However, when the oscillator is keyed Off, the D.C. voltage on the electrodes rapidly rises to substantially the value of B." "It nuns D.C. rise which purer te is efiective as a quench potential inthe registerof Fig. l'7," and quenching "is desired just subsequent to the removal "of an "energizing potential from an electrode.

' It is cleatghowever, that when the oscillator is again keyed On, there is a D.C. drop on the electrodes which is alsoiefiective as a quench potential. ,This is undesirable because, in this event, the quench potential is operating against the energizing potential; i.e., the energizing potential operates .to ionize the gas while at the same time the'd'rop in D.C. level operates to quench or disperse the ionization. It has been found that for a change in D.C. potential to be effective as a quench potential the change must be quite rapid. Thus, what is desired is a rapid change in D.C. level when an oscillator is keyedj Off and a relatively slow D.C. change when an oscillator is lteyed On. This is accomplished by a circuit comp sing a capacitor 151 (Fig. 18) having :one end connected to a junction 153 between coil and resistor 148,"and having its other endconnected through a resistor and a'diode 149, in parallel, to ground.

1 When the oscillator is keyed 011, the D.C. voltage at junction;153, and thus at'terminal 146, rises rapidly to substantially the value of the supply +B, since the effect of capacitor 151 is limited by resistor 150. When the oscillator is keyed On, the potential at junction .153 tends to drop; however, through diode 149, the capacitor 151 is now effective to decrease the rate of fall of the potential at junction 152 and therefore to decrease the rate of potential change on the electrodes.

The relationship of the energizing potentials and the direct currentpotentials on the electrodes is illustrated in the timing diagram (Fig. 19') of a one-cycle shift sequence of the; device "or Fig. 17. For example, when the energizing potential on electrodes 125 (E is removedpthe DlC. potential on these electrodes rises rapidly asillu strate d by E However, when the en- ;ergining potential E returns, the concurrent drop of E g5 iS SlOvV. An alternate typeot quench potential generator 1s shown in Fig. 20. It includes, basically, a pulse-excited, parallel resonant tuned circuit comprising a coil '169'in parallel with a'capacitor 166 in the plate circuit of a tr iode 165. Thetriode is biased'to cutofi by apotential source 164, and, is driven through a pulse transformer I63. "Thus', a pulse on an input terminal 161 is amplified by j'the itri'ode the amplified pulse excites the timed circuit. fTheosefllation of-the tuned circuit is damped ata controlledjrate bya resistor-172 in parallel 167 to an'output terminal 168. The damped wave outrminal 16ers illustrated in Fig. 21. The conwith' capacitor "166, "and 's, coupled through a"capacitor "siderations'as tdfrequency and-amplitude of AC. quench 55 'potentials'previously discussed are pertinent here.

The initial'amplitude of-the damped wave must be low enough not tocause appreciable ionization, and the frequency "must be-low enough to cause displacement oscillations er suflicientniagnitude to sweep-out and diffuse the glow 20, particularly oil-resistor discharge plasma; The parameters of the circuit of Fig. 172,m'ay be adjusted to give the desired damping rate.

"The dampediwave' quench generator may be employed -as a low 'i:'1e'quency'= generator M74, 75 and 76 in the1circuits of Figs. 5 andi8. The damping ratemay bead- .justed so that'the amplitude of the damped wavefalls to about one-third iofrits initial value between input pulses register circuit ofFig. 13.

to the individual dampedwave generatonl' "The damped wave generator may also be effectively employed in the i :In thiscase'it replaces both trigger fcircuit'92 -aud;{D.C. amplifier 91. The output of diodes 941-is'conn'ected'to the input terminal 161 of the dampedwav'e generator and the output terminal of the damped wave generator is connected directly to the reference electrode (Fig. 513') ilt-is to beinoted" that many other different combinations 

